The period between the 17th of Tammuz and the 9th of Av on the Jewish calendar is referred to as “The Three Weeks.” This period commemorates the time when the Romans invaded Jerusalem until the destruction of the HolyTemple in 70 CE. The First Temple was destroyed on the same day (the 9th of Av), and many tragedies in Jewish History occurred during this time. The three weeks is considered to be a time of mourning. It is customary to refrain from listening to music (except if we are putting on a tape or CD for children), buying new clothing and celebrating weddings and other special occasions (except for a brit, or a circumcision ceremony, and other occasions which are required to be celebrated within a specific time frame.)
This period is considered to be an unlucky one, and it is suggested to avoid court cases during the three weeks. Parents and teachers should refrain from disciplining their children too harshly during these days and from losing their tempers (these things are generally to be avoided, but especially now). Quarrels also should be guarded against, and promoting harmony among friends and acquaintances is encouraged.
Many have the custom of learning the laws governing the construction of the Holy Temple during this time, because we are not simply mourning the destruction of the Temples, but we are hoping that the Third Temple will be rebuilt and that the Messiah will come soon. It is said that, when the Messiah is revealed, these days will be transformed from unfortunate days of sadness to days of celebration. While it is proper to adopt an attitude of solemnity and awe during these days, one should not become overly despondent or depressed, because we are also meant to hope for a better time, and long for deliverance of the world, which will occur very soon.